Method of attaching shoe soles



July 3, 1934. A. L. MURRAY 1,965,297

METHOD OF ATTA CHING SHOE SOLES Filed April 25, 1932 "(VENTOR ATTO RNE Y IIY Patented July 3, 1934 UNITED STATES PATENT OFFICE 1,965,291 METHOD OF ATTACHING SHOE SOLES Albert L. Murray, Auburn, Ind.

Application April 25, 1932, Serial No. 607,486

4 Claims. (01. 12-142) The invention relates to improvements in the method of attaching shoe soles, heels and the like and it utilizes certain features set forth in my previous Patents No. 1,577,349 issued March 5 16, 1926, for Processes for securing rubber to leather and like materials, No. 1,624,500 issued April 12, 1927, for Composite rubber soles, and in my Patent No. 1,630,445 issued May 31, 1927, for Shoe bottoms.

As a result of my said inventions and the economy of the product, soles for shoes attached by these methods are now widely used, the sales being several million pairs per year. In the use and application of the article, specific and different conditions have arisen which have-necessitated new methods, based on partial useof the above inventions, combined with certain new steps necessary to produce the desired result in each case.

One such specific condition is that where it is preferred to use a leather sole instead of rubber. Various types of cement are used for the attaching of leather full-soles and half-soles to shoebottoms, either by cement alone, or in combination with sewing or nails. In all methods known to me the principal reliance for holding power, is on the strength of the cement. I have found that some provision for absorbing or taking up of the flexing motion of the shoe has a greater bearing on the obtaining of a satisfactory holding power than has the nature of the cement.

The object of my invention, therefore, is to provide a method of attaching a leather sole to a leather shoe bottom which shall result in a union having a maximum holding power and absorb the flexing motion of the shoe in walking.

In the accompanying drawing Figure 1 is an edge view of two pieces of leather joined together; Fig. 2 is an edge view of said pieces in flexed position; Fig. 3 is an edge view of two pieces of leather cemented together by a thin film of cement and partly separated; Fig. 4 is an edge view of two pieces of leather secured together by a comparatively thick film of rubber and Fig. 5-is an edge view of two partly separated pieces of leather secured together by an elastic and comparatively stifl rubber.

The leather used in the bottom of a shoe outersole, mid-sole and inner sole, is necessarily of a stifi nature in order that rocks and similar objects stepped upon will not bereadily felt therethrough. When these stiff materials are fastened together it follows that the flexing movement must take place somewhere within the structure, and that it will naturally take place to the largest degree in any part of the structurewhich may be softest and yield easiest.

In Fig. 1, the two pieces of leather 1, 2 are joined together along the line 3 and in Fig. 2 said pieces are additionally secured together at 60 their rear ends by nails or other attaching means 4. The flexing of the united pieces will cause one of them, to separate to some extent from the other and break the union between them.

In the applying of leather full-soles or half- 65 soles the cement used must be of a water-proof nature and it may be divided into two general classes: first: cement made of raw rubber dissolved in a solvent or natural rubber latex, and second: cement made of celluloid or similar materials dissolved in a suitable solvent. Nearly all of the first coat of either of these cements penetrates into the fibres of the leather and the surface film of dried material deposited by a second or even a third coat is extremely thin.

Where rubber cement is used in either of the above types mentioned, a pulling apart of the two pieces of leather will show that the legs of the rubber which have to be broken'to produce separation are of very small diameter and only about 1 inch long when stretched to the break-- ing point. This is illustrated in Figure 3, in which the pieces of leather 1, 2 have been joined, by rubber. 8 represents very short legs of rubber produced by the cement film. The holding 5 power of such a union on an inch-wide strip being only about five pounds.

I have found, and this is the basis of my present invention, that by applying a sheet of raw rubber of material thickness, such as .005 of an 90 inch, between the materials to be joined, I greatly increase the holding power, the first eifect being that most of the flexing takes place within the soft, yielding and elastic structure of this raw rubber sheet, so that only a very small part of the flexing strain ever reaches or pulls upon the impregnation of the cement in the leather. By the term raw rubber as used herein is meant crude rubber, such asvhas been formed by the coagulation of the sap of the rubber tree, which has been subjected to a milling or kneading operation until the entire mass of crude rubber, which in its natural state is heterogeneous, is rendered thoroughly homogeneous. And second, because of the material thickness of the raw rubber, the legs developed in attempts to pull it apart, are of large diameter, and elongate to about of an inch before tearing. This is illustrated in Figure 4, in which 1, 2 illustrate the cemented materials; 5 indicates the long legsf before no breaking, and 6 indicates the material thickness of cement which takes up the flexing motion. I have foundthat, by this method, I obtain a test strength on an inch wide strip of about 10 pounds.

Where celluloid, or similar cements are used in place of rubber, the cement, after evaporation, becomes comparatively hard and inelastic. This condition increases as the water base solvents, such as acetone, gradually dry out. The result is that the flexing strain is concentrated principally on the leather fibres, which are immediately adjacent to this comparatively hard cement film. And since leather fibres are not difficult to pull apart, particularly on the flesh side of the leather, the result is that separation comes about ve y easily, not by the tearing of the cement, but by the tearing of the leather. My test on an inch wide strip, after such cements have dried out-by age, such as the time between the making of a shoe and its use, is not materially different than the separation test obtained by rubber cement alone. This is illustrated in Figure 5, in which 1 and 2 are the two cemented-materials, the jagged face lines of which indicate that separation has occurred by splitting of the leather in the piece 1 while the cement line 7 has remained unbroken. I

The object of my invention being to produce union to stand up under the flexing of a shoe, I accomplish said object by the placing of a sheet of raw rubber between the two pieces of leather, the opposed surfaces of which leather are coated with cement and press them together. The surfaces of the raw rubber become homogenous with the cement surfaces with which they contact.

To avoid the extreme edge strain which often occurs by the stubbing of the toe, particularly in children's shoes, and-the possible separation of the sole and shoe bottom, I preferably bevel the edge of the applied sole in cases where it is applied on the top of the original sole. This also prevents the edge of the sole from appearing heavy.

What I claim is:

l. The process of attaching shoe soles and the like which consists in applying rubber cement to the opposed surfaces of the objects to be joined, inserting a sheet of raw rubber between the said cement coated surfaces and pressing the objects together.

2.=The process of attaching a leather sole to a shoe bottom which consists in applying rubber cement to the opposed surfaces of the sole and bottom, inserting a sheet of raw rubber between said cemented surfaces and pressing the sole and shoe bottom together.

3. The process of attaching a leather sole to a leather shoe bottom which consists in coating the opposed surfaces of the sole and shoe bottom with an adhesive capable of homogeneously uniting with raw rubber, inserting a sheet of raw rubber between said surfaces and pressing the same together.

4. The process of attaching shoe soles and the like which consists in applying rubber cement to the opposed surfaces of the objects to be joined, inserting a thin sheet of raw rubber between the cement coated surfaces, said cement being of a type homogeneously uniting with said sheet, and

pressing the objects together.

ALBERT L. MURRAY. 7 

